Red phosphors for solid state lighting

ABSTRACT

A red phosphor composition in combination with a semiconductor light emitting device (e.g., VCSEL, LED, or LD), preferably a GaN based device, that emits light at a bright violet-blue light range, i.e., having a wavelength in the range of 400 nm to 600 nm, which can be further combined with green and blue phosphors. The red phosphor composition in the combination is a vanadate combined with yttrium, gadolinium and/or lanthanum and activated with trivalent Eu 3+ , Sm 3+  and Pr 3+ , or any combination thereof, with or without Tb 3+  as a co-dopant, has the general formula: Bi x Ln 1−x VO 4 :A where x=0 to 1, Ln is an element selected from the group consisting of Y, La and Gd, and A is an activator selected from Eu 3+ , Sm 3+  and Pr 3+ , or any combination thereof, with or without Tb 3+  as a co-dopant. Novel red phosphor compositions are provided when x is greater than 0 and less than 1, preferably 0.05 to 0.5.

FIELD OF THE INVENTION

The invention is in the field of phosphors for solid state lighting.

BACKGROUND OF THE INVENTION

Recently, solid-state lighting based on GaN semiconductors has maderemarkable breakthroughs in efficiency. GaN-based diodes emit brightviolet-blue light, which can be used to pump longer wavelengthphosphors. The first white light emitting diodes (LEDs) becamecommercially available in 1997. These white LEDs can be obtained bycombining a InGaN blue LED emitting at 465 nm with a broad-band yellowphosphor, e.g. (Y_(1−x)Gd_(x))₃(Al_(1−y)Ga_(y))₅O₁₂ (YAG:Ce). Thevariation of x and y can be used to produce a broad emission from 510 nmand 580 nm, leading to a high color rendering index. These white LEDshave efficiencies comparable to incandescent lights and are provinguseful in a wide variety of niche lighting applications.

White light can be produced by a variety of other approaches, includingcolor mixing of three LED emissions (e.g., combining discrete blue,green, and red LEDs) or the pumping of phosphors with a deep blue/UV LEDor laser diode (LD). Nitride-based vertical cavity surface emittinglasers (VCSELs), coupled with phosphors optimized for violet or near-UVabsorption, offer the greatest potential for high-efficiency solid-statelighting [D. A. Steigerwald, et al]. However, the problem lies in theunavailability of suitable RGB phosphors that are optimized forabsorbing the near UV or violet emission from the LEDs or lasers. Thered, green and blue phosphors that are currently used in conventionalfluorescent lighting have been optimized for excitation by the UVemission from a mercury discharge, for which the characteristicwavelengths are 185 and 254 nm [G. Blasse, et al, 1994]. Hence, thechallenge for the new generation of lighting based upon GaN lies in thedevelopment of novel families of phosphors that are optimized forexcitations at longer wavelengths in the near UV (350–400 nm).

The current phosphor materials of choice for the solid-state lightinginitiative are Y₂O₂S:Eu³⁺ for red, ZnS:(Cu⁺, Al³⁺) for green, andBaMgAl₁₀O₁₇:Eu²⁺ (BAM) for blue [M. Shinoya, et al]. Unfortunately, thered emission with Y₂O₂S:Eu³⁺ is inadequate in comparison with the greenand blue phosphors, both in terms of its efficiency and its stability,so there is an urgent need to make superior red phosphors.

BRIEF SUMMARY OF THE INVENTION

The present invention provides new phosphors absorbing in near UV andemitting in the red by using materials that have broad and intensecharge-transfer (C-T) absorption bands in the near UV and are thereforecapable of efficiently capturing the emission from a GaN-based LED or LDover a range of wavelengths. Vanadates, combined with selectedlanthanides or yttrium, are used, optionally with bismuth, where theoxygen to metal charge-transfer bands are very intense. Following theexcitation in the UV, the energy is transferred to an activator ion by anon-radiative mechanism. More particularly, the activator ion isselected from Eu³⁺, Sm³⁺, and Pr³⁺ and any combination thereof, alone orco-doped with Tb³⁺ as an intensifier to enhance transfer. While the redphosphor materials generally should not absorb any of the green or blueemissions, a colored phosphor that converts some of the blue or green tored can have some advantages and are, therefore, not excluded.

More particularly, the invention provides a novel red phosphorcomposition as well as its combination with a light emittingsemiconductor device (e.g., VCSEL, LED, or LD), preferably a GaN baseddevice, that emits light having a wavelength in the range of 200 nm to620 nm. The composition can contain at least one non-red phosphor inaddition to the red phosphor, preferably green and blue phosphors (suchas the ZnS:(Cu⁺, Al³⁺) and BaMgAl₁₀O₁₇:Eu²⁺ phosphors described above).The red phosphor absorbs the light of a wavelength in the range of 240nm to 550 nm and emits red light at a wavelength in the range of 580 nmto 700 nm, and is a vanadate combined with yttrium, gadolinium and/orlanthanum and activated with trivalent Eu³⁺, Sm³⁺ and Pr³⁺, or anycombination thereof, with or without Tb³⁺ as a co-dopant. When combinedwith a light emitting semiconductor device, the red phosphor compositionof this invention has the general formula:Bi_(x)Ln_(1−x)VO₄:Awhere x=0 to 1, Ln is an element selected from the group consisting ofY, La and Gd, and A is an activator selected from Eu³⁺, Sm³⁺ and Pr³⁺,or any combination thereof, with or without Tb³⁺ as a co-dopant. Novelred phosphor compositions are provided when x is greater than 0 and lessthan 1, preferably 0.05 to 0.5.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the powder X-ray diffraction patterns ofsamples of Bi_(x)Y_(1−x)VO₄:Eu;

FIG. 2 is a graph showing the photoluminescence spectra ofBi_(x)Y_(1−x)VO₄:Eu samples (λ_(exc)=365 nm);

FIG. 3 is a graph showing the excitation spectra of Bi_(x)Y_(1−x)VO₄:Eusamples for the 614 nm Eu³⁺ emission;

FIG. 4 is a graph showing the excitation spectra of Bi_(x)Gd_(1−x)VO₄:Eusamples for the 613 nm Eu³⁺ emission;

FIG. 5 is a graph showing the excitation spectra of Bi_(x)La_(1−x)VO₄:Eusamples for the 612 nm Eu³⁺ emission;

FIG. 6 is a graph showing the photoluminescence spectra ofBi_(x)Y_(1−x)VO₄:Sm samples (λ_(exc)=363.8 nm); and

FIG. 7 is a graph showing the excitation spectra of Bi_(x)Y_(1−x)VO₄:Smsamples for the 645 nm Sm³⁺ emission.

DETAILED DESCRIPTION OF THE INVENTION

The light emitting device of the present invention can be any GaN basedLED, LD or VCSEL that emits light, preferably monochromatic, at awavelength in the range of 200 nm to 620 nm. Such devices are well known[M. Shinoya, et al and D. A. Steigerwald, et al], but the red phosphorused in prior devices is inadequate.

In according with the present invention, particularly useful for redphosphors are materials of the general formula:Bi_(x)Ln_(1−x)VO₄:Awhere x is a number equal to or larger than 0 but smaller than 1, Ln isan element selected from the group consisting of Y, La and Gd, and A isan activator selected from Eu³⁺, Sm³⁺ and Pr³⁺, or any combinationthereof, with or without Tb³⁺ as a co-dopant. In a preferred embodiment,particularly useful are yttrium vanadates containing Eu³⁺ (f⁶), whichfluoresces via a ⁵D₀ to ⁷F₂ transition at ˜612 nm when the ion ispresent in a non-centrosymmetric site. Eu-doped YVO₄, is used as acathodoluminescent material in color television screens, and isappropriate for the present application, since the C-T band of thevanadate ion is well placed in the UV.

In a preferred embodiment, it is useful to incorporate Bi³⁺ in which6s²→6s6p excitations in the bismuth ion can also be used to harvest thenear-UV light. In the case of the Bi_(x)Ln_(1−x)VO₄ (Ln=Gd, Eu,) system,for example, structural and spectral studies have shown the existence oftwo ranges of solid solution [Ghamri, et al., 1990; Ghamri, et al.,1989]. One has a tetragonal structure of the zircon type (0<x<0.64) andthe other has a monoclinic structure of the scheelite-relatedfergusonite type (x>0.93). Coordination of the cations in these oxidesis such that V is coordinated to four oxygen atoms forming a tetrahedronand Ln (or Bi) to eight oxygen atoms from different tetrahedra. In thepresent embodiment we have utilized the luminescence behavior of thesolid solutions of Bi_(x)Ln_(1−x)VO₄:A, where Ln and A are as definedabove and 0<x<1, and correlated it with the available structuralinformation. In addition, we have also investigated the effect ofco-doping with Tb, e.g., Tb(III)/Pr(III) on the Eu(III) emission inthese solid solutions and compare the emission intensities of thesesamples with the standard red phosphor (Y₂O₂S:Eu³⁺).

The red phosphors of the present invention are excited by light of 240to 550 nm and emits light of 580 to 700 nm which peaks at ˜610 to 650nm. The Bi_(x)Ln_(1−x)VO₄:A composition is obtained by mixing oxides,carbonate and the like of elements which constitute the phosphor at adesired stoichiometric ratio. The red phosphor can be combined withgreen and blue phosphors, e.g., respectively, ZnS:(Cu⁺, Al³⁺) andBaMgAl₁₀O₁₇:Eu²⁺ phosphors. The combination of phosphors can be appliedas a layer to a light emitting semiconductor device such as a VCSEL, LEDor LD. For example the combination can be applied as a layer to a GaNdie and encapsulated by a lens typically formed of a transparent epoxy.In operation, electrical power is supplied to the GaN die to activateit, which then emits light that activates the phosphors to emit outputlight of combined wavelengths and which will vary depending on thespectral distribution and intensities of the light emitted from thephosphors. See, for example, the description of the prior art phosphorLED in Lowery, et al. U.S. Pat. No. 6,351,069, the disclosure of whichis incorporated herein by reference. The present invention enables theemitted wavelengths to have a combined spectral distribution such thatit appears to be “white” light.

In a preferred embodiment, the combination of a red phosphor of thisinvention and prior art green and blue phosphors are such that the whitelight is obtained having a combination of spectral ranges of 500 to 580nm (green), 400 to 500 nm (blue), and 580 to 700 nm (red).

EXAMPLES 1–9

Syntheses of red phosphors in accordance with this invention werecarried out by firing well ground samples of rare earth oxide, bismuthoxide and NH₄VO₃ in an alumina crucible at 600° C. for 24 h. Theproducts were then removed from the furnace, cooled, finely ground andreheated at 800° C. for another 24–48 h to complete the reaction. Insome cases, another round of regrinding was needed. The rare-earthvanadate compounds are white powders (yellow or orange when there isunreacted vanadium oxide), which become yellowish with increasingBi-content. The dopant atoms were Eu³⁺ (added as Eu₂O₃) and Sm³⁺ (addedas Sm₂O₃) and the doping concentration was about 5 mol % (of theLn³⁺+Bi³⁺) in each of the syntheses. The final products werecharacterized by powder X-ray diffraction, photoluminescence andphotoexcitation spectroscopy.

X-ray diffraction studies on Bi_(x)Ln_(1−x)VO₄ samples doped with Eu³⁺

Structural studies of the system Bi_(x)Gd_(1−x)VO₄ have shown theexistence of two ranges of solid solution, as described above [Ghamri,et al., 1990]. The study of the mixed LnVO₄—BiVO₄ (Ln=Y, Gd, La) samplesdoped with Eu³⁺ samples shows the expected change in the XRD patternwith increasing bismuth concentration (FIG. 1). Samples with x≦0.65 showa powder pattern corresponding to the tetragonal zircon phase (FIG. 1a–d), whereas for x>0.65 the powder pattern indicates that these samplescontain a mixture of both monoclinic fergusonite and tetragonal zirconphases (FIG. 1 e,f). The pure BiVO₄ doped with Eu³⁺ shows the powderpattern corresponding to the monoclinic form (FIG. 1 g).

Spectral Properties of Bismuth-Rare-Earth Vanadates Doped with Eu³⁺

In general, the photoluminescence spectra of YVO₄—BiVO₄ doped with Eu³⁺ions show strong ⁵D₀→⁷F₂ (614, 618 nm) and ⁵D₀ ⁷F₁ (593 nm) emissionlines on excitation at both 254 nm and 365 nm (FIG. 2). The excitationspectrum for monitoring the ⁵D₀→⁷F₂ emission of Eu³⁺ shows a broadcharge-transfer band along with a sharp ⁷F₀→⁵L_(6,) Eu³⁺ line at 394 nm,the latter being a relatively weak spectral feature when compared to thebroad C-T band (FIG. 3). The excitation spectrum in pure YVO₄ doped withEu³⁺ shows a broad absorption maximum centered around ˜310 nm, and aband edge at 340 nm, however the absorption in the short-wavelength UV(240–275 nm) is very low. In the case of Bi_(x)Y_(1−x)VO₄:Eu³⁺ the bandedge shifts to longer wavelengths with increasing bismuth concentration.For example, the band edge in the excitation spectrum moves from 340 nm(for pure YVO₄, x=0) to ˜420 nm for the x=0.45 bismuth rich sample (FIG.3). This increase occurs due to extra absorption involving the Bi—Ocomponent in addition to the V—O charge-transfer bands. This increaseseems to be monotonic only when less than half (x=0.4–0.45) of theyttrium ions are substituted by Bi³⁺ ions. For substitutions exceedingmore than half (x>0.45) of yttrium by Bi³⁺, the long-wavelengthcharge-transfer band diminishes in intensity and disappears completelyfor compositions with x>0.65; however, the absorption in theshort-wavelength (240–275 nm) appears to increase gradually (FIG. 3).

The photoluminescence spectra of GdVO₄—BiVO₄ doped with Eu³⁺ again showthe characteristic spectral lines for Eu³⁺ emission. The excitationspectrum for monitoring the ⁵D₀→⁷F₂ emission of Eu³⁺ shows a smallabsorption in the short-wavelength region (240–275 nm), a broadcharge-transfer band at lower energies, and a sharp but weak ⁷F₀→⁵L_(6,)Eu³⁺ line at 394 nm (FIG. 4). The excitation spectrum in pure GdVO₄doped with Eu³⁺ shows a band edge at 350 nm, but in theBi_(x)Gd_(1−x)VO₄:Eu³⁺ system the band edge shifts to longer wavelengthswith increasing bismuth concentration, moving to ˜425 nm for the x=0.4sample (FIG. 4). Again, this increase seems to be monotonic only whenless than half (x=0.4) of the gadolinium ions are substituted by Bi³⁺ions. For substitutions exceeding x=0.4, the long-wavelengthcharge-transfer band again decreases in intensity, as in the yttriumsystem, though the short-wavelength (240–275 nm) absorption increasesgradually.

The photoluminescence spectra of LaVO₄—BiVO₄ doped with Eu³⁺ also showsimilar trends in luminescence properties with increasing bismuthcontent to those observed for yttrium-bismuth/gadolinium-bismuthvanadates (FIG. 5).

Spectral Properties of Bismuth-Yttrium Vanadates Doped with Sm³⁺

Sm⁺³ as an activator in YVO₄ is known to have high emission efficiency.There is also considerable similarity in the emission colors of bothSm³⁺ (orange red) and Eu³⁺ (red) in the vanadate lattice. Thephotoluminescence spectra YVO₄—BiVO₄ doped with Sm³⁺ ions show the mainemission lines for Sm⁺³ are 564 (⁴G_(5/2)-⁶H_(5/2)), 601(⁴G_(5/2)-⁶H_(7/2)) and 645, 654 nm (⁴G_(5/2)-⁶H_(9/2)) on excitation at363.8 nm (FIG. 6). The excitation spectrum for monitoring the⁴G_(5/2)→⁶H_(9/2) emission of Sm³⁺ shows a weak absorption band at shortwavelengths (240–275 nm), a broad charge-transfer band centered around˜320 nm, plus the sharp Sm³⁺ lines (FIG. 7). The excitation spectrum inpure YVO₄ doped with Sm³⁺ shows a broad maximum centered around ˜320 nmwith a band edge at 350 nm. In the case of Y_(1−x)Bi_(x)VO₄:Sm³⁺ samplesthe charge-transfer band and the band edge shift to longer wavelengthswith increasing bismuth concentration. As the bismuth concentrationincreases the band edge in the excitation spectrum moves from 340 nm(for pure YVO₄x=0) to ˜415 nm for (x=0.4) bismuth rich samples. As withthe other systems described above, this increase seems to be monotoniconly when less than half (x=0.4) of the yttrium ions are substituted byBi³⁺ ions. For substitutions exceeding x>0.45 of yttrium by Bi³⁺ ionsthe long-wavelength charge-transfer band decreases drastically inintensity, whereas the absorption at short wavelengths (240–275 nm)increases gradually (FIG. 7).

In Table 1, we list the comparison of emission intensities of theBi_(x)Y_(1−x)VO₄:Eu³⁺ ions to that of the standard Y₂O₂S:Eu³⁺ redphosphor on excitation at 400 nm. The samples containing lowconcentrations of Bi³⁺ show a decreased Eu³⁺ emission when compared tothat of the standard red phosphor when excited at 400 nm, whereas thesamples containing bismuth x≧0.2 show a much enhanced emission, thehighest being in sample containing bismuth x=0.3. The increase in theemission intensity of Eu³⁺ with Bi³⁺ content is due the energy transferfrom Bi³⁺ center to Eu³⁺. Increased bismuth content decreases theefficiency of this energy transport from the matrix to Eu³⁺, perhaps bydistorting the former. Such distortions may arise from the chemical andelectronic nature of Y³⁺ and Bi³⁺ ions.

TABLE 1 Comparison of emission intensities of the Y_(1−x)Bi_(x)VO₄:Eu³⁺ions to that of the standard Y₂O₂S:Eu³⁺ red phosphor Example CompositionEmission Intensity (λ_(exc) = 400 nm) Y₂O₂S:Eu (standard) 3.3 1Y_(0.95)Eu_(0.05)VO₄ 0.13 2 Y_(0.90)Bi_(0.05)Eu_(0.05)VO₄ 0.15 3Y_(0.85)Bi_(0.10)Eu_(0.05)VO₄ 0.12 4 Y_(0.75)Bi_(0.20)Eu_(0.05)VO₄ 0.725 Y_(0.70)Bi_(0.25)Eu_(0.05)VO₄ 0.77 6 Y_(0.65)Bi_(0.30)Eu_(0.05)VO₄ 1.27 Y_(0.60)Bi_(0.35)Eu_(0.05)VO₄ 0.81 8 Y_(0.55)Bi_(0.40)Eu_(0.05)VO₄0.97 9 Y_(0.50)Bi_(0.45)Eu_(0.05)VO₄ 0.71

The Bi_(x)Y_(1−x)VO₄ samples codoped with Eu³⁺,Tb³⁺ or Eu³⁺, Pr³⁺ ionsalso show a similar comparison to the standard red phosphor when theiremission intensities were measured at 400 nm. No energy transfer fromthe Tb³⁺ or Pr³⁺ was observed as expected in the beginning, though thereasons to this effect are still unclear. Further study in this regardis under progress.

Datta, et al. showed that for the YVO₄:Eu, Bi system, increasing amountof Bi³⁺ ions in the lattice, the excitation bands shift to longerwavelengths. The 6s²→6s6p transition of Bi³⁺ ions often contributes tothe luminescence of bismuth-doped phosphors [Blasse, et al. 1968]. Webelieve that the extra absorption and the band shift towards longerwavelengths in the excitation spectrum of LnVO₄—BiVO₄ samples doped withEu³⁺ or Sm³⁺ involves the absorption due to Bi³⁺ ions. Such extraabsorption has also been witnessed in other cases when ns² ions havebeen introduced in other host lattices absorbing in the UV region, forexample, CaWO₄—PbWO₄ [Blasse, et al. 1994], Y₂WO₆—Bi [Blasse, et al.1968]. The more puzzling observation however, is that the excitationspectra of the Bi_(1−x)Ln_(x)VO₄ samples doped with Eu³⁺ or Sm³⁺ show adecrease in the long wavelength absorption above a critical bismuthconcentration. Literature reports on bismuth, antimony niobates andtantalates have concluded that if ns² ions are in a more favorableasymmetrical coordination, the outer electrons (ns²) tend to be morelocalized and stabilized, so their influence on the luminescence of thesurrounding centers is smaller [Wiegel, et al.]. The excitation spectraof the samples with low bismuth content (x≦0.4) can be explained by thefact that Bi³⁺ ions are present in a more symmetrical (zircon-type)environment, and hence the 6S² electrons are on top of the 2p level ofO²⁻ as a result of which the excitation band shifts to longerwavelengths. Beyond a certain limit increasing bismuth content(0.4<x<0.64), we observe a drastic reduction in the long-wavelengthabsorption in the excitation spectra, even though the samples are stillwith in the composition regime of the zircon phase (0<x<0.64). Theluminescence behavior of the Bi_(1−x)Ln_(x)VO₄:Eu/Sm samples with0.4<x<0.64 must stem from distortion of the bismuth environments as moreBi is introduced into the zircon structure.

EXAMPLES 10–19

Syntheses of other red phosphors having the general formula:Bi_(x)Ln_(1−x)VO₄:A, where x=0 to 1, Ln is an element selected from thegroup consisting of Y, La and Gd, and A is an activator selected fromEu³⁺, Sm³⁺ and Pr³⁺, combination thereof, with or without Tb³⁺ as aco-dopant can be synthesized using the procedure of Examples 1–9. Thus,well ground samples of rare earth oxide, bismuth oxide and NH₄VO₃ can befired in an alumina crucible at 600° C. for 24 h. The products can thenbe removed from the furnace, cooled, finely ground and reheated at 800°C. for another 24–48 h to complete the reaction, with another round ofregrinding if needed. Dopant atoms of Eu³⁺ (as Eu₂O₃), Sm³⁺ (as Sm₂O₃),and/or Pr³⁺ (Pr₂O₃) can be added at a doping concentration of about 5mol % (of the Ln³⁺ +Bi³⁺) in each of the syntheses. To some of thecompositions ˜25 to 40 ppm of Tb³⁺ can be added. The final redphosphors, which will have formulas shown in Table 2, can becharacterized by powder X-ray diffraction, photoluminescence andphotoexcitation spectroscopy.

TABLE 2 Compositions of Examples 10–19 Example Composition 10Y_(0.95)Sm_(0.05)VO₄ 11 Y_(0.95)Pr_(0.05)VO₄ 12Y_(0.90)Bi_(0.05)Sm_(0.05)VO₄ 13 Y_(0.85)Bi_(0.10)Pr_(0.05)VO₄ 14Y_(0.75)Bi_(0.20)Eu_(0.03)Sm_(0.02)VO₄ 15Y_(0.70)Bi_(0.25)Eu_(0.02)Pr_(0.03)VO₄ 16Y_(0.65)Bi_(0.30)Eu_(0.04999)Tb_(0.00001)VO₄ 17Y_(0.60)Bi_(0.35)Eu_(0.025)Pr_(0.02499)Tb_(0.00001)VO₄ 18Y_(0.55)Bi_(0.40)Eu_(0.025)Sm_(0.02499)Tb_(0.00001)VO₄ 19Y_(0.50)Bi_(0.45)Eu_(0.025)Sm_(0.01)Pr_(0.01499)Tb_(0.00001)VO₄

REFERENCES

-   Blasse, G. and A. Bril, J. Chem. Phys. 1968 48(1) 217.-   Blasse, G., and B. C. Grabmeier, Luminescent Materials,    (Springer-Verlag, Berlin, 1994).-   Datta, R. K., J. Electrochem. Soc. 1967, 114(10) 1057.-   Ghamri, J., H. Baussart, M. Lebras and J. M. Leroy, J. Phys. Chem.    Solids, 1989, 50, 1237.-   Ghamri, J., H. Baussart, M. Lebras and J. M. Leroy, Ann. Chim-Sci    Mat. 1990 15(3) 111.-   Shinoya, M., and W. M. Yen, Phosphor HandBook, (CRC Press, 1999)-   Steigerwald, D. A., J. C. Bhat, D. Collins, R. M. Fletcher, M. O.    Holcomb, M. J. Ludowise, P. S. Martin and S. L. Rudaz, IEEE. J. Sel.    Top. Quant. 2002, 8(2) 310.-   Wiegel, M., W. Middel and G. Blasse, J. Mater. Chem. 1995, 5(7) 981.

1. A light emitting semiconductor device, comprising: a GaN based lightemitting diode that emits light having a wavelength in the range of 200nm to 620 nm; a red phosphor that absorbs light of a wavelength in therange of 240 nm to 550 nm and emits red light at a wavelength in therange of 580 nm to 700 nm, having the formula:Bi_(x)Ln_(1−x)VO₄:A where x is 0.05 to 0.5, Ln is an element selectedfrom the group consisting of Y, La and Gd, and A is an activatorselected from Eu³⁺, Sm³⁺ and Pr³⁺, or any combination thereof, with orwithout Tb³⁺ as a co-dopant; a green phosphor; and a blue phosphor. 2.The device of claim 1 including Tb³⁺ as a co-dopant.
 3. The device ofclaim 1 in which said green phosphor is ZnS:(Cu⁺,Al³⁺) and said bluephosphor is BaMgAl₁₀O₁₇:Eu²⁺.
 4. A white light emitting phosphorcombination, comprising: a red phosphor having the formula:Bi_(x)Ln_(1−x)VO₄:A where x is greater than 0 and less than 1, Ln is anelement selected from the group consisting of Y, La and Gd, and A is anactivator selected from Eu³⁺, Sm³⁺, or Pr³⁺, or any combination thereof,with or without Tb³⁺ as a co-dopant; a green phosphor; and a bluephosphor.
 5. The phosphor combination of claim 4 in which said redphosphor absorbs light of a wavelength in the range of 240 nm to 550 nmand emits red light at a wavelength in the range of 580 nm to 700 nm. 6.The phosphor combination of claim 4 in which said green phosphor isZnS:(Cu⁺,Al³⁺) and said blue phosphor is BaMgAl₁₀O₁₇:Eu²⁺ suitable foruse in a GaN based device.
 7. A white light emitting phosphorcombination, a red phosphor that absorbs said light of a wavelength inthe range of 240 nm to 550 nm and emits red light at a wavelength in therange of 580 nm to 700 nm, having the formula:Bi_(x)Ln_(1−x)VO₄:A where x is 0.05 to 0.5, Ln is an element selectedfrom the group consisting of Y, La and Gd, and A is an activatorselected from Eu³⁺, Sm³⁺ and Pr³⁺, or any combination thereof, with orwithout Tb³⁺ as a co-dopant.; a green phosphor comprisingZnS:(Cu⁺,Al³⁺); and a blue phosphor comprising BaMgAl₁₀O₁₇:Eu²⁺.
 8. Thephosphor combination of claim 7 in which said red phosphor includes Tb³⁺as a co-dopant.
 9. A red phosphor that absorbs said light of awavelength in the range of 240 nm to 550 nm and emits red light at awavelength in the range of 580 nm to 700 nm , having the formula:Bi_(x)Ln_(1−x)VO₄:A where x is 0.05 to 0.5, Ln is an element selectedfrom the group consisting of Y, La and Gd, and A is an activatorselected from Eu³⁺, Sm³⁺ and Pr³⁺, or any combination thereof, with orwithout Tb³⁺ as a co-dopant.
 10. The phosphor of claim 9 in which inwhich said red phosphor includes Tb³⁺ as a co-dopant.
 11. A lightemitting device, comprising: a semiconductor device that emits lighthaving a wavelength in the range of 200 nm to 620 nm ; and a redphosphor having the formula:Bi_(x)Ln_(1−x)VO₄:A where x is 0.05 to 0.5, Ln is an element selectedfrom the group consisting of Y, La and Gd, and A is an activatorselected from Eu³⁺, Sm³⁺ and Pr³⁺, or any combination thereof, with orwithout Tb³⁺ as a co-dopant.
 12. The device of claim 11 in which thesemiconductor device is a GaN based device.
 13. The device of claim 12in which the semiconductor device is a light emitting diode.
 14. A lightemitting device, comprising: a semiconductor device that emits lighthaving a wavelength in the range of 200 nm to 620 nm; and a red phosphorcomprising a vanadate combined with yttrium, gadolinium and/or lanthanumand activated with trivalent Eu³⁺, Sm³⁺ or Pr³⁺, or any combinationthereof, with Tb³⁺ as a co-dopant.
 15. A white light emitting phosphorcombination, comprising: a red phosphor comprising a vanadate combinedwith yttrium, gadolinium and/or lanthanum and activated with trivalentEu³⁺, Sm³⁺ and Pr³⁺, or any combination thereof, with Tb³⁺ as aco-dopant; a green phosphor; and a blue phosphor.
 16. A red phosphorthat absorbs said light of a wavelength in the range of 240 nm to 550 nmand emits red light at a wavelength in the range of 580 nm to 700 nm,having the formula:Bi_(x)Ln_(1−x)VO₄:A where x is greater than 0 and less than 1, Ln is anelement selected from the group consisting of Y, La and Gd, and A is anactivator selected from Eu³⁺, Sm³⁺ and Pr³⁺, or any combination thereof,with Tb³⁺ as a co-dopant.
 17. The phosphor of claim 16 in which x is0.05 to 0.5.
 18. A light emitting GaN based device, comprising: asemiconductor device that emits light having a wavelength in the rangeof 200 nm to 620 nm; a green phosphor and a blue phosphor; and a redphosphor having the formula:Bi_(x)Ln_(1−x)VO₄:A where x is greater than 0 and less than 1, Ln is anelement selected from the group consisting of Y, La and Gd, and A is anactivator selected from Eu³⁺, Sm³⁺ and Pr³⁺, or any combination thereof,with or without Tb³⁺ as a co-dopant.
 19. A light emitting GaN baseddevice, comprising: a semiconductor device that emits light having awavelength in the range of 200 nm to 620 nm; a red phosphor having theformula:Bi_(x)Ln_(1−x)VO₄:A where x is greater than 0 and less than 1, Ln is anelement selected from the group consisting of Y, La and Gd, and A is anactivator selected from Eu³⁺, Sm³⁺ and Pr³⁺, or any combination thereofwith or without Tb³⁺ as a co-dopant; a green phosphor having theformula: ZnS:(Cu⁺,Al³⁺); and a blue phosphor having the formula:BaMgAl₁₀O₁₇:Eu²⁺.